How the Raspberry Pi Pico Enables Bluetooth Keyboards Over I²C

The Raspberry Pi Pico W can be repurposed to bridge Bluetooth keyboards to the I²C bus, letting microcontroller projects receive keystrokes as if from a legacy I²C keyboard [3]. This approach, demonstrated by Roberto Alsina’s “bt2i2c” firmware, expands the flexibility of hardware interfaces for hobbyists and developers.

Key takeaways

• The bt2i2c firmware runs on a Pi Pico W and forwards Bluetooth keyboard input to I²C [3].
• Keystrokes appear on the I²C bus with the address 0x1F, matching existing BlackBerry keyboard drivers [3].
• Adding an ST7789 display via SPI can provide visual connection status, though it’s optional [3].

Turning Bluetooth Input into I²C Data

Roberto Alsina’s project flashes custom firmware onto a Pi Pico W, enabling the board to act as a Bluetooth host for standard keyboards. Once paired, the Pico captures each key event and transmits it over the I²C bus using the address 0x1F, a convention already supported by code for BlackBerry BBQ20/BBQ10 keyboards [3]. This compatibility means developers can reuse existing I²C keyboard libraries without rewriting drivers.

Optional Visual Feedback with SPI

While the core functionality does not require a display, Alsina suggests connecting an ST7789 screen via SPI to the Pico [3]. The screen can show connection status, helping users verify that the Bluetooth pairing succeeded and that keystrokes are being relayed correctly. This addition is purely for convenience and does not affect the I²C bridging capability.

Why it matters

By converting wireless Bluetooth input into a simple I²C stream, the Pi Pico W bridges the gap between modern peripherals and legacy hardware interfaces, simplifying the design of embedded systems that rely on I²C for sensor or display communication. As microcontrollers grow more capable, such firmware solutions enable developers to reuse existing codebases and hardware, reducing development time and expanding the range of possible projects.